Extraction of hydrocarbons from a downhole drilling operation needs to be cost effective and timely. One factor to ensure this effective and timely extraction is the proper weight on the drill bit downhole (weight-on-bit) during a drilling operation. If not enough weight is applied to the drillstring, the drill bit thereon may not bore out the hole as quickly, thereby taking longer for the extraction of these hydrocarbons. This delay in extraction may translate into lost revenue.
However, if too much weight is applied to the drill string, the drill bit and other parts of the drill string may be damaged and may be lost downhole. If parts of the drill string are damaged or lost downhole during the drilling operation, the drilling operations must stop. A fishing operation typically occurs to recover these components and clear the borehole. If such components cannot be recovered and the borehole cannot be cleared, the drilling operation may need to be restarted, wherein a new borehole is created. The time lost in such situations is costly because, instead of extracting hydrocarbons from downhole, time is wasted in these recovery/restart operations.
Therefore, monitoring of the weight on the drill bit during a drilling operation is vital for the effective and timely extraction of hydrocarbons. One approach to monitor this weight includes the measurement of a length of a drill collar of the drill string. In particular, the length of the drill collar is indicative of its compression and expansion due to the weight applied thereto. Conventional approaches for the measurement of the compression and expansion of the drill collar include the use of strain gauge sensors and/or hydraulic sensors. Such sensors either measure a physical deflection or hydraulic pressures caused when the drill collar is in compression. Disadvantageously, both the strain gauge sensors and the hydraulic sensors require calibration with specialized equipment to produce accurate results. The calibration parameters for these sensors may change over time. Moreover, such sensors are subject to damage because of the stresses that may be induced thereon during drilling operations. Additionally, the hydraulic sensors may develop leaks and require periodic maintenance to replace o-rings, fluids, etc.